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Subject: Re: [PATCH v38 21/24] x86/vdso: Implement a vDSO for Intel SGX
 enclave call
To:     Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        Borislav Petkov <bp@alien8.de>
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References: <20200915112842.897265-1-jarkko.sakkinen@linux.intel.com>
 <20200915112842.897265-22-jarkko.sakkinen@linux.intel.com>
 <20200924180407.GO5030@zn.tnic> <20200925010031.GH119995@linux.intel.com>
From:   Jethro Beekman <jethro@fortanix.com>
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On 2020-09-25 03:00, Jarkko Sakkinen wrote:
> End result:
>=20
> https://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-sgx.git/tr=
ee/arch/x86/include/uapi/asm/sgx.h
>=20
> I'm wondering this sentence:
>=20
> "The calling convention is custom and does not follow System V x86-64 A=
BI."
>=20
> AFAIK, now the vDSO is fully C-callable but waiting for feedback before=

> removing it.

It's C-callable *iff your enclave follows the System V x86-64 ABI*. In ad=
dition, all registers not clobbered by the SGX ISA are passed to the encl=
ave, not just those specified as parameter passing registers in the ABI. =
This is intentional to make the vDSO function usable in applications that=
 use the current flexibility of ENCLU.

--
Jethro Beekman | Fortanix


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